Red Hot resistor

[Disco-Pete]

Apparently this is a Leach circuit from what I've gathered. Can't find the specific schematic.

 

[llwhtt]

Many amps use a 120VAC relay with no additional circuitry for this purpose but from your pics it looks as though there is some circuitry next to the relay. What is the relay voltage, AC or DC?

Craig

 

[Disco-Pete]

Many amps use a 120VAC relay with no additional circuitry for this purpose but from your pics it looks as though there is some circuitry next to the relay. What is the relay voltage, AC or DC?

Craig

24vdc

 

[llwhtt]

Are there any small electrolytic capacitors on that board? Can we get a better picture of the board? Component side and trace side.

Craig

 

[Disco-Pete]

Are there any small electrolytic capacitors on that board? Can we get a better picture of the board? Component side and trace side.

Craig

 

[llwhtt]

Do the red and blue wires go to the solder pads that appear to have nothing on top of the board? The red wire at the very bottom of the picture?

Craig

 

[jwilhelm]

Does that big power resistor say 2.5k ohm? If so that likely isn't right.

 

[Disco-Pete]

Do the red and blue wires go to the solder pads that appear to have nothing on top of the board? The red wire at the very bottom of the picture?

Craig

 

[Disco-Pete]

Does that big power resistor say 2.5k ohm? If so that likely isn't right.

Yes it does. Nothing in the amp appears to have been touched. However..?

 

[jwilhelm]

Was that the resistor that was blistered or is it another one? The close up shot can be misleading.

 

[llwhtt]

Looks like the circuit uses both B+ and B- with no ground, so the 2.5K Ohm resistor is dropping the rest of the voltage for the 24VDC relay. I'm trying to scratch out the circuit now.

Can I get a straight down shot of the board?

Craig

 

[Disco-Pete]

Was that the resistor that was blistered or is it another one? The close up shot can be misleading.

No, you can see that one above the relay in the distance.

 

[jwilhelm]

I don't see any DC protection on the output of the amp. You might want to consider replacing that board and adding a couple solid state relay boards to the speaker outputs.

 

[Disco-Pete]

Looks like the circuit uses both B+ and B- with no ground, so the 2.5K Ohm resistor is dropping the rest of the voltage for the 24VDC relay. I'm trying to scratch out the circuit now.

Can I get a straight down shot of the board?

Craig

 

[llwhtt]

I should be able to sketch out the circuit from your pics, everything but component values. Are you able to take voltage measurements, etc.?

Craig

 

[Disco-Pete]

I should be able to sketch out the circuit from your pics, everything but component values. Are you able to take voltage measurements, etc.?

Craig

Sure, you just need to tell me where to put the probes. I'm brave

I have clip-ons

 

[Disco-Pete]

Bipolar electronic systems update

First of all, Jeff Willhelm very kindly got this thing up and running way back when. He added his own proprietary protection circuit also. I just have not listened to it til just recently, I've been trying to sell it with no success on CAM. Pity the two on separate occasions who committed but didn't show up to get it. I've been listening to it for about a week now. It's no longer for sale! This is very close to the best amp I've ever heard. Very fast with excellent low level resolution without being clinical. I have tinnitus and this amp does not aggravate it at all, no fatigue at all. But the bottom end is incredible. I have not heard this level of performance with any amp before. Sharp definition on the lowest notes. No boom, not dry, just all there. Very transparent and lively. If there's an amp that should be cloned, this is one

 

[Mark Tillotson]

Ideally a soft-start resistor would be rated for continuous operation to avoid this sort of issue starting a fire. You may find the resistor value can be increased to reduce its power dissipation.
Alternatively a thermal switch could be placed above it.

 

[jwilhelm]

Good to hear it's still going strong! That amp did have a lot of punch.

 

[Disco-Pete]

Good to hear it's still going strong! That amp did have a lot of punch.

It's a great amp Jeff. But now I'm very curious about how those two pairs of Meridian 105s I mentioned to you would sound paralleled. Are you up for it?